Pressure-regulating device for a fuel consumption measurement system and fuel consumption measurement system

ABSTRACT

A pressure-regulating device for a fuel consumption measurement system includes a fuel supply line which supplies fuel to a consumer, a fuel return line, a bypass line which branches off from the fuel supply line, a pressure regulator which sets a free flow cross-section in the bypass line, a pressure sensor arranged at the fuel supply line downstream of where the bypass line branches off, a control unit electrically connected to the pressure sensor, and a pressure-reducing element arranged in the fuel supply line upstream of the pressure sensor and downstream of the branch of the bypass line. The bypass line fluidically connects the fuel supply line to the fuel return line and feeds fuel from the fuel supply line to the fuel return line while bypassing the consumer. The pressure sensor provides pressure measurement values. The control unit regulates the pressure regulator depending on the pressure measurement values.

The invention relates to a pressure-regulating device for a fuelconsumption measurement system having a fuel supply line which isconnectable to a consumer and through which fuel is adapted to besupplied to the consumer, a fuel return line through which fuel isadapted to be returned, a bypass line through which the fuel supply lineis fluidically connected to the fuel return line and through which fuelis adapted to be guided from the fuel supply line to the fuel returnline bypassing the consumer, and a pressure regulator through which afree flow cross-section is adapted to be set in the bypass line, as wellas a fuel consumption measurement system having a fuel supply linethrough which a tank is fluidically connected to a consumer and throughwhich fuel is adapted to be supplied from the tank to the consumer via afirst fuel pump, a flowmeter in the fuel supply line, a fuel return linewhich is fluidically connected to the tank or the fuel supply linedownstream of the flowmeter and through which fuel is adapted to bereturned to the tank or into the fuel supply line downstream of theflowmeter, a feed pump in the fuel supply line downstream of theflowmeter.

Fuel consumption measurement systems are usually constituted of a modulecarrying out the actual fuel measurement performed via flowmeters, suchas Coriolis meters, for example, or parallel-connectedpiston/displacement meter units, such as described in DE-AS 1 798 080,for example, and, for measurement systems comprising a fuel return line,additionally include a conditioning module via which a constant pressureis set in the fuel supply line.

These systems for fuel consumption measurement with apressure-regulating device are arranged in front of the fuelhigh-pressure pump of a common-rail system of an internal combustionengine having a plurality of injection valves. These are either closedcircuits where the fuel is fed from the fuel return line downstream ofthe actual measurement device back into the fuel supply line, or systemswhere a return line extending directly to the tank is provided in whicha second flowmeter is arranged such that the fuel consumption can becalculated from the difference of the two flowmeters.

An exact measurement requires the fuel to be supplied at a constantsupply line pressure to the consumer which is in particular an internalcombustion engine with common rail injection. Hence, it is commonpractice to arrange a pressure regulator configured as an overflow valvein the bypass line, which valve regulates the pressure in the bypassline and thus indirectly the pressure in the fuel supply line in that anincreasing flow cross-section in the bypass line leads to an increase ofthe free flow cross-section. This regulation is however passive suchthat flow-independent changes of the pressure gradient are not takeninto consideration, whereby errors in the consumption measurement due topressure variations occur. In addition, it is not possible to generate asupply line pressure of 0 bar or a vacuum pressure, which is howeverrequired depending on the operating condition.

For this reason, active pressure-regulating devices have been developedwhere, in addition to the pressure regulator in the bypass line, anotherpressure regulator configured as a pressure reducer is arranged in thefuel supply line. While the pressure regulation in the positive pressurerange is continued to be performed via the overflow valve, at a setpointof the supply line pressure in the negative range the pressure reducer,which is in its completely open position without any pressure actingupon it, can be moved into a position in which it throttles or evencloses the flow cross-section such that an increased pressure drop isgenerated due to which a vacuum pressure can be generated in thesubsequent spur line. The necessary operating pressure for this pressurereducer can be built up by means of the overflow valve.

Such a configuration has however the drawback that two regulatingelements are necessary for realizing zero pressures or vacuum pressureswhich further have a mutual effect on each other, whereby an exactregulation of the supply line pressure to a constant actual valuebecomes difficult. Accordingly, the capital expenditure for realizingsuch a pressure regulation is high.

It is thus an object to provide a pressure-regulating device as well asa fuel consumption measurement system by means of which an as exact aspossible setting of the supply line pressure to a constant setpoint canbe achieved with a minimum number of apparatus and at minimum expense,and as large as possible a pressure range can be set which also includes0-pressures or vacuum pressures as supply line pressures relative to theatmospheric pressure. By means of such a pressure-regulating devicereproducible measurement results are to be obtained by maintaining thesame measurement conditions.

This object is achieved with a pressure-regulating device for a fuelconsumption measurement system having the features of claim 1 as well asa fuel consumption measurement system having the features of claim 12.

Due to the fact that the flow regulating unit comprises a pressuresensor that is arranged at the fuel supply line downstream of the branchof the bypass line, that is electrically connected to a control unit viawhich the pressure regulator is adapted to be regulated as a function ofthe measurement values of the pressure sensor, wherein an unregulatedpressure-reducing element is arranged in the fuel supply line upstreamof the pressure sensor and downstream of the branch of the bypass line,an exact setpoint of the supply line pressure can be adjusted via thepressure regulator and the number of apparatus can be minimized sinceonly one control element is necessary. In addition, a pressure belowatmospheric pressure or atmospheric pressure can be set via thepressure-reducing element without any additional control elements beingnecessary. The active regulation and pressure measurement lead to anexact setting of the measurement conditions and hence to reproduciblemeasurement results.

Accordingly, the object is also achieved with a fuel consumptionmeasurement system which uses such a pressure-regulating device whosebypass line branches off the fuel supply line downstream of theflowmeter and enters the fuel return line. Such a fuel consumptionmeasurement system supplies very exact measurement values across a widesetpoint spectrum with a minimum number of apparatus.

Preferably, the pressure-reducing element is a check valve which, on theone hand, prevents a return flow and, on the other hand, generates apressure drop that is constant to a large extent but depends on thecurrent flow velocities, such that negative pressures in the fuel supplyline can be generated with simple means when the pressure regulator isplaced into a state in which the flow cross-section in the bypass lineis wide open.

According to an alternative embodiment of the invention, thepressure-reducing element is a throttle or an orifice. These components,too, generate a pressure drop between their inlet and their outlet, dueto which pressure drop the settable pressure range can also be set tonegative pressures in the subsequent fuel supply line section.

Preferably, the pressure regulator is a spring-loaded regulating valve.The spring can either load a regulating body of the regulating valveinto a state in which the regulating cross-section of the valve isclosed or into a state in which it is opened. Opening or closing is thenperformed only when a sufficient counterforce is generated by means ofwhich the spring force is overcome. When using a valve closed by springforce, an adequate fuel supply of the internal combustion engine isensured even when the valve fails, since the fuel would be completelyfed to the internal combustion engine.

According to a preferred embodiment, the regulating valve is apneumatically operable valve. The air pressure for such a valve caneither be provided via a separate pressure container, via pressureconnectors at the internal combustion engine or via pressure connectorsin the building equipment. These valves have a very low powerconsumption while offering a very good regulating capability. Inaddition, pneumatically operated valves are less susceptible to failuresince no fuel can enter electric components, in which case corrosionand, in extreme cases, explosions could occur when the fuel comes ontocontact with the electronic system.

The pneumatic pressure for operating the control valve is advantageouslyregulated by means of an electric pilot valve which is controlled viathe control unit. Said valve can in particular be adapted to beelectromagnetically operated, wherein the electromagnet is supplied withcurrent depending on the comparison of the actual values of the pressuresensor with its setpoints and hence provides a correspondingly regulatedpressure for operating the pneumatic pressure regulator.

Alternatively to these embodiments, the pressure regulator can also beconfigured as an electric regulating valve which is controlled via thecontrol unit and directly regulates the flow cross-section. In thismanner, an additional component is saved.

According to another advantageous embodiment of the invention, thepressure-reducing element is adapted to be bypassed via a circuitousline. Hence, the complete pressure provided by the feed pump can also beused as the supply line pressure for the consumer although the staticpressure-reducing element is arranged in the fuel supply line. Thus, thepressure range, within which measurements can be taken, is furtherincreased.

According to another embodiment, a two-way valve is arranged at abranch-off of the circuitous line branching off the fuel supply line, bymeans of which valve thus switching between the two lines is possible ina simple manner.

In addition, the pressure-regulating device is adapted to be fluidicallyconnected, downstream of the pressure sensor and upstream of theconsumer, to a feed pump which is usually configured as a high-pressurepump and hence is suitable for generating a negative pressure in thefuel supply line.

Preferably, the bypass line enters the fuel return line through whichunconsumed fuel is adapted to be returned into the pressure-regulatingdevice. In particular in the case of diesel engines with directinjection, a considerable amount of fuel can hence be partly returned inparticular from the distributor pipe of the common rail system.

Hence, according to a preferred embodiment, in the fuel consumptionmeasurement system in particular for diesel applications, the fuelreturn line branches off the fuel supply line or a distributor pipe ofthe consumer downstream of the pressure-regulating device and enters thepressure-regulating device upstream of a place where the bypass lineenters the fuel return line.

Thus, a pressure-regulating device for a fuel consumption measurementsystem as well as fuel consumption measurement system having such apressure-regulating device are provided by means of which temporallyresolved flow processes can be determined with high precision and in acontinuous manner in that an exact supply line pressure in the fuelsupply line can be measured and regulated in accordance with thesemeasurement values. Hence, errors caused by different flow velocities inthe case of purely passive elements are reliably avoided. In addition,these measurements can be performed across a large pressure range whichalso includes negative pressures below atmospheric pressure. For thispurpose, merely one regulating element is necessary such that the numberof apparatus and thus the number of components and the costs can bereduced.

The fuel consumption measurement system according to the inventionhaving the pressure-regulating device according to the invention isillustrated in the Figures and will be described hereunder on the basisof the Figures.

FIG. 1 shows a flow chart of a fuel consumption measurement deviceaccording to the invention having a pressure-regulating unit accordingto the invention.

FIG. 2 shows a pressure regulator of the pressure-regulating unitaccording to the invention.

The fuel consumption measurement system according to the invention iscomposed of a tank 10 where fuel is stored. From this tank 10, fuel ispumped into a fuel supply line 14 by means of a first fuel pump 12. Thefuel supply line 14 extends to a consumer 16 which is configured as aninternal combustion engine 18 having a common rail injection system inthis exemplary embodiment. Accordingly, the fuel supply line 14 extendsto feed pump 20 configured as high-pressure pump which forms part of theinternal combustion engine and via which the fuel is fed into a commonrail distributor pipe 22 and compressed. The distributor pipe 22 isfluidically connected to injection valves 24 through which the fuel isinjected into the combustion chambers of the internal combustion engine18.

Usually, in these systems, larger fuel amounts are fed than are actuallyinjected through the injection valves 24 such that a fuel return line 26branches off the distributor pipe 22, said fuel return line extendingback to the fuel supply one 14. The returned fuel amounts can be amultiple of the injected fuel amounts.

For measuring the fuel consumption, a flowmeter 28 is arranged in thefuel supply line 14. Said flowmeter can be realized as a Coriolis meter,for example, or by parallel connection of a displacement meter having amovable piston, for example. In the fuel supply line 14, the rotatorydisplacement meter is arranged for measuring purposes, whichdisplacement meter is driven by means of a drive motor. In a pistonchamber, a piston displaceable in an inertia-free manner is arranged inthe parallel line to the displacement device. A change of the volumetricflow in the fuel supply line 14 first results in a deflection of thepiston, which deflection is measured by means of a path sensor. Themeasurement values are provided to a control unit which receives thevalues and transmits corresponding control signals to the drive motorthat is controlled such that the piston is always returned into itsdefined initial position, the volumetric flow thus being discharged asexactly as possible via the rotatory displacement device. Since a volumefed during a time interval can be associated with each speed of therotatory displacement device, it is possible to calculate a fuelconsumption from these values.

The flowmeter measures the fuel consumption in the fuel supply line 14.The fuel return line 26 extending back to the fuel supply line 14 entersthe fuel supply line 14 downstream of the flowmeter 28 and upstream of afeed pump 29 for preventing this fuel from being measured twice andbeing able to feed this fuel. When the consumer 16 takes up only a smallamount of fuel, merely small amounts of fuel need be supplied to themeasurement system through the fuel pump 12, which is why upstream ofthe flowmeter 28 another return line 30 branches off the fuel supplyline 14, through which fuel can be returned to the tank 10 when asufficient pressure prevails in the fuel supply line 14. In this furtherreturn line 30, a mechanical pressure regulator 31 is arranged for thispurpose, via which the pressure in front of the flowmeter 28 is set. Itwould also be possible to regulate the pressure behind the flowmeter 28via this mechanical flowmeter 31.

An exact fuel consumption measurement can be performed only when aconstant supply line pressure prevails in the fuel supply line 14immediately in front of the high-pressure pump 20. According to theinvention, this is achieved with a pressure-regulating device 32comprising a bypass line 34 which branches off the fuel supply line 14and enters the fuel return line 26, wherein the branch is arrangeddownstream of the flowmeter 28 and downstream of the place where thefuel return line 26 enters the fuel supply line 14 and of the feed pump20. In this bypass line 34, a pressure regulator 36 configured as aregulating valve is arranged. This pressure regulator 36 comprises aregulating body 38 which is urged away from its valve seat 42 towardsthe opening of the flow cross-section by a spring 40. In the presentcase, this pressure regulator 36 is pneumatically closed by introducinga pressure into a pressure chamber 44 which is defined by a membrane 46connected to the regulating body 38, wherein the pressure acts, counterto the spring force, on the membrane 46, whereby the regulating body 38is lowered to its valve seat 42 surrounding the flow cross-section oncethe product of the applied pressure and the surface of the membrane 46is larger than the force of the spring 40.

In addition, the pressure-regulating device 32 is constituted of anunregulated, that is static pressure-reducing element 48 which isconfigured as a check valve in the present exemplary embodiment, but canalso be configured as a throttle or an orifice, and is arranged in thefuel supply line 14 downstream of a branch 50 of the bypass line 34. Viathis pressure-reducing element 48, a pressure drop between its outletand its inlet occurs which merely depends on the flow velocity but isconstant to a large extent.

This pressure-reducing element 48 can be bypassed via a circuitous line52. For this purpose, a branch-off 54 is provided directly upstream ofthe pressure-reducing element 48, in which branch-off a 3/2-way valve 56is arranged that serves for ensuring that the supplied fuel optionallyeither flows via the pressure-reducing element 48 and further throughthe fuel supply line 14 or through the circuitous line 52 bypassing thepressure-reducing element 48. The circuitous line 52 enters the fuelsupply line 14 again directly downstream of the pressure-reducingelement 48.

Downstream of the pressure-reducing element 48, and also downstream ofthe place where the circuitous line 52 enters the fuel supply line 14 inthe present exemplary embodiment, but upstream of the feed pump 20, apressure sensor 58 is arranged at the fuel supply line 14, via whichsensor the supply line pressure in the fuel supply line 14 is measured.This pressure sensor 58 converts the pressure into a correspondingelectric signal which is supplied to a control unit 60. This controlunit 60 serves for controlling an electric pilot valve 62 via which apressure from a pressure container 64 or another pressurized-air supplysource is controlled and supplied to the pressure sensor 36 or thepressure chamber 44 of the pressure regulator 36. Accordingly, thepressure regulator 36 in the bypass line 34 is regulated depending onthe difference between the actual values of the pressure sensor 58 andsetpoints transmitted to the control unit 60.

If a central controller determines that the fuel consumption is to bemeasured at a supply line pressure of 1 bar in the fuel supply line 14,but the actual value measured by the pressure sensor 58 is only 0.5 bar,the pressure regulator 36 is shifted further into a closed state in thatthe pilot valve 62 increases the pressure fed into the pressure chamber44. Thus, the pressure in the fuel supply line 14 increases up to thedesired setpoint. If smaller setpoints are specified, they may be belowatmospheric pressure since the already low pressure prevailing in frontof the pressure-reducing element 48 when the pressure regulator 36 isfully open is further reduced due the pressure drop occurring at saidpressure-reducing element and hence may be decreased to 0 bar or even−0.5 bar. If particularly high setpoints are required, the pressureregulator 36 can be fully closed and additionally the two-way valve 56can be switched such that no pressure drop occurs via thepressure-reducing element 48. This bypassing of the pressure-reducingelement 48 can even take place at pressures as from approximately 1.5bar in order to reduce the load acting on the feed pump 29.

Thus, the pressure-regulating device 32 according to the inventionallows exact fuel consumption measurements across a large pressure rangeto be performed. These consumption measurements can be performed both atmaximum feed pressures of the feed pump and at low feed pressures whichcan be further down-regulated to −0.8 bar at the fuel supply line. Thefuel pressure setpoint is thus set by the electronic control loop in avery short time taking into consideration the actual value of thepressure determined by the pressure sensor such that high regulationaccuracy and velocity are achieved. This leads to very exact andreproducible measurement results of the fuel consumption measurementsystem such that measurements can repeatedly be taken at exactly definedmeasurement conditions and then compared. Due to the simpleconfiguration of the regulating units used and the small number ofelements to be regulated, the necessary number of apparatus and thus theexpense are reduced as compared to prior art actively regulatingpressure-regulating devices.

It is appreciated that the invention is not limited to the describedexemplary embodiment and various modifications within the scope ofprotection of the main claim are possible. In particular, it isconceivable that instead of the pneumatic pressure regulator a hydraulicor purely electric pressure regulator can be used. Hence, the controlunit of an electric regulating valve can be used with the values of thepressure sensor for direct electric control of the regulating valve, forexample. Further, it is understood that various configurations of fuelconsumption measurement systems are known where this pressure-regulatingdevice can be used. Hence, in particular, the section of the fuel returnline upstream of the mouth of the bypass line is omitted in the case ofgasoline applications where no increased fuel feed with return flow fromthe distributor takes place.

1-13. (canceled)
 14. A pressure-regulating device for a fuel consumptionmeasurement system, the pressure-regulating device comprising: a fuelsupply line which is configured to be connected to a consumer and viawhich a fuel is suppliable to the consumer; a fuel return line via whichthe fuel is returnable; a bypass line comprising a branch which branchesoff from the fuel supply line, the bypass line being configured tofluidically connect the fuel supply line to the fuel return line and tofeed the fuel from the fuel supply line to the fuel return line whilebypassing the consumer; a pressure regulator which is configured to seta free flow cross-section in the bypass line; a pressure sensor arrangedat the fuel supply line downstream of where the branch of the bypassline branches off from the fuel supply line, the pressure sensor beingconfigured to provide pressure measurement values; a control unit whichis electrically connected to the pressure sensor, the control unit beingconfigured to regulate the pressure regulator depending on the pressuremeasurement values of the pressure sensor; and an unregulatedpressure-reducing element arranged in the fuel supply line upstream ofthe pressure sensor and downstream of the branch of the bypass line. 15.The pressure-regulating device as recited in claim 14, wherein theunregulated pressure-reducing element is a check valve.
 16. Thepressure-regulating device as recited in claim 14, wherein theunregulated pressure-reducing element is a throttle or an orifice. 17.The pressure-regulating device as recited in claim 14, wherein thepressure regulator is a spring-loaded regulating valve.
 18. Thepressure-regulating device as recited in claim 17, wherein thespring-loaded regulating valve is pneumatically operable.
 19. Thepressure-regulating device as recited in claim 18, further comprising:an electric pilot valve, wherein, the control unit is further configuredto control the electric pilot valve, and a pneumatic pressure foroperating the spring-loaded regulating valve is regulated via theelectric pilot valve.
 20. The pressure-regulating device as recited inclaim 14, wherein the pressure regulator is an electric regulating valvewhich controlled by the control unit.
 21. The pressure-regulating deviceas recited in claim 14, further comprising: a circuitous line which isconfigured to bypass the pressure-reducing element.
 22. Thepressure-regulating as recited in claim 21, further comprising: a 3/2valve, wherein, the circuitous line comprises a branch which branchesoff from the fuel supply line (14), and the 3/2 valve is arranged at thebranch.
 23. The pressure-regulating device as recited in claim 14,further comprising: a feed pump arranged downstream of the pressuresensor (58) and upstream of the consumer in the fuel supply line,wherein, the pressure-regulating device is configured to be fluidicallyconnected to the feed pump.
 24. The pressure-regulating device asrecited in claim 14, wherein, the bypass line is configured to enterinto the fuel return line, and the fuel return line is configured toreturn the fuel which is not consumed to the pressure-regulating device.25. A fuel consumption measurement system comprising: a fuel supply linewhich is configured to fluidically connect a tank to a consumer and viawhich a fuel is supplied from the tank to the consumer via a first fuelpump; a flowmeter arranged in the fuel supply line; a fuel return linewhich is fluidically connected to the tank or to the fuel supply linedownstream of the flowmeter and via which the fuel is returnable to thetank or into the fuel supply line downstream of the flowmeter; a feedpump arranged in the fuel supply line downstream of the flowmeter; andthe pressure-reducing device as recited in claim 14, wherein, the bypassline of the pressure-reducing device branches off from the fuel supplyline and enters the fuel return line downstream of the flow meter. 26.The fuel consumption measurement system as recited in claim 25, whereinthe fuel return line is configured to branch off from the fuel supplyline or from a distributor pipe of the consumer downstream of thepressure-regulating device and to enter the pressure-regulating deviceupstream of where the bypass line enters the fuel return line.